The communications and cable television industries almost exclusively utilize fiber optic or coaxial cables. These cables are often laid underground beneath streets and sidewalks. Typically, backbone conduit systems are laid beneath streets, and lateral connections are taken off the backbone conduits to buildings or utility poles. The lateral connections in particular use cables having small diameters, usually less than one inch.
Backbone conduit systems are laid using a traditional open cut trench method or a large horizontal boring technique. In the open cut trench method, a trench is dug is the street and/or sidewalk along the conduit""s route. The conduit is laid in the trench, and the trench is backfilled.
In the large horizontal boring technique, two large pits are dug. A large boring machine is lowered into the first pit, the sending pit, which then bores a pathway underground to the second pit, the receiving pit.
When a lateral is needed from an existing manhole in the backbone system, the open cut trench method is used almost exclusively. In this method, an open trench is cut in the street and/or sidewalk to a depth of two to three feet. A four-inch conduit is laid in the trench. The fiber optic cables are pulled through the conduit. The trench is then backfilled.
Since the breakup of the monopolistic telecommunications industry in 1984, many new entrants have begun to compete with the established telecommunication companies, the Regional Bell Operating Companies (RBOCs).
These new companies, Competitive Local Exchange Carriers (CLECs) may request the leasing of backbone conduits from the RBOCs, which under federal law the RBOCs must provide. The CLECs still have to get their facilities off of the RBOCs"" backbone conduit network to buildings or pole lines in some manner. Even when the CLECs build their own backbone conduit system, they must provide lateral connections to buildings or poles.
Many cities and towns have adopted a lead company policy for telecommunication companies. This lead company policy provides that, if a company wants to dig the city or town streets, it must notify all potential telecommunication and cable TV companies of its intent, and ask them if they wish to participate in the xe2x80x9cdig.xe2x80x9d This policy is intended to minimize the number of times that a street is dug. All interested parties share the costs proportionately. The lead company policy may have a negative effect on individual companies, however, in that it reveals to competitors where companies are building their networks. Additionally, once a city or town has newly repaved a street, it usually puts a five-year bond on that street and does not permit the street to be disturbed again, prohibiting cable TV and telecommunications companies from digging the street to provide their services.
The open cut trench method has other disadvantages as well. Excavation of streets and sidewalks results in the disruption of their original condition. Settlement is possible, creating a rut that may be a hazard to motor vehicles and pedestrians. The excavation may hit or damage an existing utility beneath the surface. In many instances, the work must be performed at night in urban locations due to motor vehicle congestion. Steel plating of all or partial lengths of the open trench must be provided to allow vehicular traffic to pass and pedestrian access for street crossing or building access.
Horizontal directional boring from within an existing utility manhole with working sensitive communication cables is presently not commercially available. The existing commercial large boring machines are not suitable for boring from within a manhole. Also, because existing manholes contain live, working cables, great caution must be exercised when any machinery is lowered into the manhole. This need for great caution discourages the placing of machinery or equipment into manholes.
The present invention relates to a mobile subterranean horizontal directional boring capability from within an existing utility manhole to buildings, to other manholes, and to utility poles, or from utility poles to manholes. The invention is particularly suitable for laying small diameter fiber optic cabling without the need for open cut trench excavation. The invention provides for protection of the manhole during the boring operation, so that existing equipment and facilities in the manhole are not damaged.
All of the machinery to provide the subterranean boring is mounted on a mobile vehicle that may be driven to the work site. The boring machinery includes a boring unit supported on the platform or bed of the vehicle. The boring machinery also includes an arm assembly, which may include an articulated arm or a flexible chute, through which boring rods are sequentially fed. The arm assembly leads from the boring unit to an opening within the manhole. The arm assembly is fastened to a containment unit provided within the opening in the manhole wall. In this manner, the integrity of the working CATV and telecommunications equipment and any other equipment present in the manhole is protected. A manhole rim protection unit is also provided around the manhole rim and secured to the manhole chimney.
The boring unit is operable up to at least a 60xc2x0 tilt from level. In the preferred embodiment, it is sized to provide torque and thrust specifications to manage a two-inch bore for up to 400-foot distances. Rod flexibility specifications allow for a ten-foot radius. The boring unit and arm assembly are secured to a rotating turntable or lazy susan on the platform on the rear of the truck bed to allow pivoting of up 180xc2x0. Pivoting allows for truck work site positioning in congested areas to allow for the proper direction of the bore.